Ink jet printers are a very common type of household printer. The ink jet printer ejects droplets of ink from a set of nozzles onto a recording medium, such as a paper, by oscillating a piezo element or by boiling the ink. For fineness of printing, the current ink jet printers are designed to eject extremely minute droplets of ink, as small as a few to a few dozen picoliters.
As the ink droplets become smaller, they tend to fly unstably when ejected. In addition, fine mists of ink are also ejected. These mists are extremely small droplets, but when accumulated, they will cause a problem. Especially, when the mists accumulate on a platen which supports a sheet of recording medium horizontally flat, they contaminate the next recording medium, and lower print quality.
Some of the ink jet printers provide duplex printing capability. In the duplex printing process, a recording medium is reversed when an image has been printed on the front surface thereof, and then an image is printed on the rear surface. During this process, the front surface of the recording medium with the image printed is fed (conveyed) to slide on the platen, and leaves the ink to contaminate the platen. The contamination of the platen could be prevented if the recording medium is fed to the platen after the ink on the front surface had penetrated and fixed (dried) completely. In the recent years with growing demand for high speed printing, however, it is a common practice to start printing on the rear surface before the ink on the front surface has completely fixed.
Under this circumstance, a cleaning sheet is conventionally used to remove ink stain on the platen. Made of a special material, this type of cleaning sheet is expensive. Therefore, there is disclosed a method of removing ink stain on the platen with use of an inexpensive recording medium, such as a regular paper (see, for example, Japanese Patent Laid-open Publication No. 2004-25666). According to this method, a recording medium is moved back and forth with the front end thereof touching the upper surface of the platen, so as to wipe off the dirt, or ink stain, on the platen during feeding.
However, this method may be of little effect when the front end of the recording medium is deformed for some reasons, and fails to touch the platen. This problem may be solved by bending a part of the recording medium into a downward projection, and wiping the platen with this downward projection. This approach, however, requires a user to bend the recording medium. In addition, this approach may lead to misbending or overbending which cause jamming or other errors in feeding the recording medium.